feat: initial fediverse registration/login

Foxnouns.Backend/Services/Auth/AuthService.cs

@@ -1,4 +1,5 @@
 using System.Security.Cryptography;
+using Foxnouns.Backend.Controllers.Authentication;
 using Foxnouns.Backend.Database;
 using Foxnouns.Backend.Database.Models;
 using Foxnouns.Backend.Utils;
@@ -6,10 +7,17 @@ using Microsoft.AspNetCore.Identity;
 using Microsoft.EntityFrameworkCore;
 using NodaTime;
 
-namespace Foxnouns.Backend.Services;
+namespace Foxnouns.Backend.Services.Auth;
 
-public class AuthService(IClock clock, DatabaseContext db, ISnowflakeGenerator snowflakeGenerator)
+public class AuthService(
+    IClock clock,
+    ILogger logger,
+    DatabaseContext db,
+    ISnowflakeGenerator snowflakeGenerator,
+    UserRendererService userRenderer
+)
 {
+    private readonly ILogger _logger = logger.ForContext<AuthService>();
     private readonly PasswordHasher<User> _passwordHasher = new();
 
     /// <summary>
@@ -256,6 +264,45 @@ public class AuthService(IClock clock, DatabaseContext db, ISnowflakeGenerator s
         );
     }
 
+    /// <summary>
+    /// Generates a token for the given user and adds it to the database, returning a fully formed auth response for the user.
+    /// This method is always called at the end of an endpoint method, so the resulting token
+    /// (and user, if this is a registration request) is also saved to the database.
+    /// </summary>
+    public async Task<CallbackResponse> GenerateUserTokenAsync(
+        User user,
+        CancellationToken ct = default
+    )
+    {
+        var frontendApp = await db.GetFrontendApplicationAsync(ct);
+
+        var (tokenStr, token) = GenerateToken(
+            user,
+            frontendApp,
+            ["*"],
+            clock.GetCurrentInstant() + Duration.FromDays(365)
+        );
+        db.Add(token);
+
+        _logger.Debug("Generated token {TokenId} for {UserId}", user.Id, token.Id);
+
+        await db.SaveChangesAsync(ct);
+
+        return new CallbackResponse(
+            HasAccount: true,
+            Ticket: null,
+            RemoteUsername: null,
+            User: await userRenderer.RenderUserAsync(
+                user,
+                selfUser: user,
+                renderMembers: false,
+                ct: ct
+            ),
+            Token: tokenStr,
+            ExpiresAt: token.ExpiresAt
+        );
+    }
+
     private static (string, byte[]) GenerateToken()
     {
         var token = AuthUtils.RandomToken();

Foxnouns.Backend/Services/Auth/FediverseAuthService.Mastodon.cs

@@ -5,12 +5,12 @@ using Foxnouns.Backend.Database.Models;
 using Duration = NodaTime.Duration;
 using J = System.Text.Json.Serialization.JsonPropertyNameAttribute;
 
-namespace Foxnouns.Backend.Services;
+namespace Foxnouns.Backend.Services.Auth;
 
 public partial class FediverseAuthService
 {
     private string MastodonRedirectUri(string instance) =>
-        $"{_config.BaseUrl}/auth/login/mastodon/{instance}";
+        $"{_config.BaseUrl}/auth/callback/mastodon/{instance}";
 
     private async Task<FediverseApplication> CreateMastodonApplicationAsync(
         string instance,

Foxnouns.Backend/Services/Auth/FediverseAuthService.cs

@@ -4,7 +4,7 @@ using Microsoft.EntityFrameworkCore;
 using NodaTime;
 using J = System.Text.Json.Serialization.JsonPropertyNameAttribute;
 
-namespace Foxnouns.Backend.Services;
+namespace Foxnouns.Backend.Services.Auth;
 
 public partial class FediverseAuthService
 {
@@ -43,12 +43,6 @@ public partial class FediverseAuthService
         return await GenerateAuthUrlAsync(app);
     }
 
-    public async Task<FediverseUser> GetRemoteFediverseUserAsync(string instance, string code)
-    {
-        var app = await GetApplicationAsync(instance);
-        return await GetRemoteUserAsync(app, code);
-    }
-
     // thank you, gargron and syuilo, for agreeing on a name for *once* in your lives,
     // and having both mastodon and misskey use "username" in the self user response
     public record FediverseUser(
@@ -56,7 +50,7 @@ public partial class FediverseAuthService
         [property: J("username")] string Username
     );
 
-    private async Task<FediverseApplication> GetApplicationAsync(string instance)
+    public async Task<FediverseApplication> GetApplicationAsync(string instance)
     {
         var app = await _db.FediverseApplications.FirstOrDefaultAsync(a => a.Domain == instance);
         if (app != null)
@@ -110,7 +104,10 @@ public partial class FediverseAuthService
             _ => throw new ArgumentOutOfRangeException(nameof(app), app.InstanceType, null),
         };
 
-    private async Task<FediverseUser> GetRemoteUserAsync(FediverseApplication app, string code) =>
+    public async Task<FediverseUser> GetRemoteFediverseUserAsync(
+        FediverseApplication app,
+        string code
+    ) =>
         app.InstanceType switch
         {
             FediverseInstanceType.MastodonApi => await GetMastodonUserAsync(app, code),

Foxnouns.Backend/Services/UserRendererService.cs

@@ -97,7 +97,7 @@ public class UserRendererService(
             ? $"{config.MediaBaseUrl}/users/{user.Id}/avatars/{user.Avatar}.webp"
             : null;
 
-    public string ImageUrlFor(PrideFlag flag) => $"{config.MediaBaseUrl}/flags/{flag.Hash}.webp";
+    private string ImageUrlFor(PrideFlag flag) => $"{config.MediaBaseUrl}/flags/{flag.Hash}.webp";
 
     public record UserResponse(
         Snowflake Id,